Vehicles are typically equipped with an air conditioning system to provide cabin cooling and to dry air for dehumidifying functions. Air conditioning systems typically include a compressor driven by a vehicle's internal combustion engine. The compressor can be either engaged, fully or partially, or disengaged to the engine via an electronically controlled clutch.
During air conditioning system operation under certain operating conditions, the compressor cycles between an engaged and disengaged state. Cycling is typically controlled based on refrigerant pressure in the air conditioning system. When the engine and clutch are coupled, pressure decreases and significantly cooled cabin air is circulated through the vehicle. Such operation continues until pressure reaches a minimum value where the clutch is controlled to disengage the engine and compressor. If air circulation is continued, pressure increases until it reaches a maximum value. At this maximum value, the compressor is then re-engaged via the clutch and cycling repeats.
The inventors herein have proposed engaging the compressor at time other than when pressure reaches a maximum value. However, a potential disadvantage with this approach is that the compressor could be engaged too soon after it was previously disengaged. If this occurred the compressor could only be engaged a short duration and excessive cycling could result.